A coherent phonon-induced hidden quadrupolar ordered state in Ca₂RuO₄
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1.
California Institute of Technology
Abstract
AbstractUltrafast laser excitation provides a means to transiently realize long-range ordered electronic states of matter that are hidden in thermal equilibrium. Recently, this approach has unveiled a variety of thermally inaccessible ordered states in strongly correlated materials, including charge density wave, ferroelectric, magnetic, and intertwined charge-orbital ordered states. However, more exotic hidden states exhibiting higher multipolar ordering remain elusive owing to the challenge of directly manipulating and detecting them with light. Here we demonstrate a method to induce a dynamical transition from a thermally allowed to a thermally forbidden spin-orbit entangled quadrupolar ordered state in Ca₂RuO₄ by coherently exciting a phonon that is strongly coupled to the order parameter. Combining probe photon energy-resolved coherent phonon spectroscopy measurements with model Hamiltonian calculations, we show that the dynamical transition is manifested through anomalies in the temperature, pump excitation fluence, and probe photon energy dependence of the strongly coupled phonon. With this procedure, we introduce a general pathway to uncover hidden multipolar ordered states and to control their re-orientation on ultrashort timescales.
Copyright and License
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Acknowledgement
We thank Min-Cheol Lee and Jong-Seok Lee for sharing optical conductivity data. Time-resolved optical spectroscopy measurements and model Hamiltonian calculations were supported by an ARO PECASE Award No. W911NF-17-1-0204. D.H. acknowledges support for instrumentation from the David and Lucile Packard Foundation and the Institute for Quantum Information and Matter, an NSF Physics Frontiers Center (PHY-1733907). M.B. acknowledges support from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy Cluster of Excellence Matter and Light for Quantum Computing (ML4Q) EXC 2004/1 390534769, and by the DFG Collaborative Research Center (CRC) 1238 (Project No. 277146847, subproject C04) and CRC 183 (Project No. 277101999, subproject B02). Work at C.U. Boulder is supported by the National Science Foundation via Grant No. DMR 2204811.
Contributions
These authors contributed equally: Honglie Ning, Omar Mehio, Xinwei Li.
H.N., X.L, O.M., and D.H. conceived the experiment. X.L. and H.N. performed the coherent phonon spectroscopy measurements. H.N. and M.B. developed the many-body theory and conducted the dynamical simulations. H.N., X.L, and O.M. analyzed the data. M.D. conducted the DFT simulations. H.Z. and G.C. synthesized and characterized the samples. H.N. and D.H. wrote the manuscript with input from all authors.
Data Availability
Source data are provided with this paper. All other data that support the findings of this study are available from the corresponding author upon request. Source data are provided with this paper.
Conflict of Interest
The authors declare no competing interests.
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Additional details
- United States Army Research Office
- W911NF-17-1-0204
- David and Lucile Packard Foundation
- National Science Foundation
- PHY-1733907
- Deutsche Forschungsgemeinschaft
- EXC 2004/1 390534769
- Deutsche Forschungsgemeinschaft
- CRC 1238 277146847-C04
- Deutsche Forschungsgemeinschaft
- CRC 183 277101999-B02
- National Science Foundation
- DMR-2204811
- Caltech groups
- Institute for Quantum Information and Matter